The invention relates to a fuel supply system for an internal combustion engine having a fuel tank for liquid fuel, a fuel storage unit and a device for separating low boiling fuel fractions from the fuel for storage in the storage unit.
A fuel supply system of this type is known from DE 197 34 493 C1. This fuel supply installation is provided with a fuel tank for liquid fuel, from which a fuel feed line leads to an injection apparatus, with an evaporation and condensing device for low boiling-point fuel fractions, which is connected to the fuel tank, with an intermediate tank for the condensate, connected after the evaporation and condensing device, from which a condensate line leads to a control valve controlling the supply to the injection device, and with a residual fuel return line discharging the higher boiling-point residual fuel fractions accumulating in the evaporation and condensing device. The residual fuel return line opens into an additional tank, from which a residual fuel feed line leads to a changeover valve arranged in the fuel feed line. The control of the valve is such that, under full load of the internal combustion engine, the residual fuel from the residual fuel feed line is at least partly fed into the fuel feed line leading to the injection device.
Because of emission limits established world-wide nowadays, with statutorily prescribed exhaust gas emission limiting values, a fuel supply system having a fuel fractionation device for producing low boiling-point fuel fractions is needed in a motor vehicle operated with internal combustion engines, in order to reduce the pollutant emissions during the operation of a motor vehicle in the cold-start and/or warm-up phase and to reduce the discharge of pollutant overall. Such systems are frequently complicated in terms of apparatus and of design and therefore need a large overall volume with a corresponding overall weight.
It is therefore an object of the invention to provide a fuel supply system for an internal combustion engine which has only a low overall volume and a low overall weight in conjunction with a reduced pollutant emission during the various operating phases of the motor vehicle.